Burner safety control apparatus for air heaters



Oct. 18, 1955 SPACKMAN 2,720,916

BURNER SAFETY CONTROL APPARATUS FOR AIR HEATERS Filed Aug. 7, 1951INVENTOR.

THOMAS F. SPACKMAN ATTORNEY United States Patent 2,720,916 BURNERSAFET'YcoN'TiroL APPARATUS FOR AIR HEATERS Thomas Fred Spackman, Cincinnati,()hio, assignor to American Air FiIticampaiiy, In'c., Louisville, K a

corporatioho'f Delaware Application August 7, 1951, Serial No. 240,747 1Claiin. c1. 158-28) The present invention relates to a portablecombustion type air heater employing kerosene or similar liquid fuel,and relates in particular to the control mechanism for operating theheater unit.

It is an object of the present invention to provide a scavenging controlin an air heater employing an air supply, and ignition and combustioncontrol circuits, whereby the ignition and combustion control circuitsmay be placed in operation only after a period of operation of the airsupply, and on shutting down the heater, the ignition and combustioncontrol circuits may be shut off before the air supply stops.

The invention will be explained in detail in the following descriptiontaken in connection with the accompanying drawing illustrating apreferred embodiment of the invention by way of example, and wherein:

Figure l is a perspective view of a portion of the heater;

Figure 2 is a perspective view on an enlarged scale of the motor, blowerand fan assembly; and

Figure 3 is a diagrammatic view of the invention.

Referring to the drawing, the heater is carried on a chassis supportedby a pair of wheels 1 at one end and provided with a foot at the otherend. By raising the foot end by means of suitable handles, the heatermay be wheeled to any desired location. The wheeled end of the chassishas a platform 2 upon which is mounted the electric motor 3. A blowerhousing 4 for combustion air is suitably mounted on the platform, andthe motor shaft 5 extending through the housing carries a blower in thehousing and a fan 6 for supplying air to be heated by a suitable heatexchanger (not shown). The heater casing has an opening 7 shrouding fan6 so that the fan forces air through the opening to the heat exchangerin the casing and the heated air discharged at the front end of thecasing is conducted by suitable detachable ducts to any desiredlocation. The fuel pump 8 is driven by the motor through a drive pulley9 and belt (Figure 3) to supply fuel to the burner through a pressureopened valve 16 (Figure 3), and the blower housing 4 has a dischargeduct 11 to supply air to the burner to support combustion.

The starting switch 12 has two contacts A and B, and a movable sweepcontactor 13. When this contactor is turned to position A the motor 3 isenergized through lead 14 and return lead 15, and motor 3 drives pump 8.The pump incorporates a bypass with a relief valve 16 controlled by asolenoid 17 and when valve 16 is open (as when solenoid 17 isdeenergized) the pump outlet pressure is not sufficient to open reliefvalve and fuel does not flow to the burner 18. However, when bypassvalve 16 is closed upon energization of the solenoid 17, pressure isbuilt up at the pump outlet sufficient to open relief valve 16 to allowflow of fuel to the burner. At the same time if igniter 19 is energizedby transformer 21 the fuel will be ignited. It should be observed thatthe solenoid 17 and transformer 21 are not directly connected to switchcontact A so that upon turning the switch to "ice 2 pisi't'ionAllie-flow of fuel to the burner is not started, but the motoiwill drivethe fan, which scavenge enmer chamber. hen the contactor 13 is 'fiivel'l'to position B, it retains contact at A so that meter 3 "cant-iniiesenergized.

A limit control switch 22 is connected between contact B and thepfirnaryeoil er transformer 23, circuit being completed by lead 2410wire 15. The seeoifilafy er the nansfonner includes lead 25 to switch-26, lead 27 to the frela'y coil 28, load 29, resistaneehea'ter 31and-"switch 32. When switch 12 is turned to position B, relay 28 isenergized to close SW-itch centa'cts '33, thus energizing the ignitiontransformer 21 ii-rough lean 34. A-t the seine time energizatien or may28 closes switch contacts 35.

The safety control for the apparatus includes the limit controlthermostat switch 22, and the thermal responsive switches 26 and 32.Switch 22 is responsive to the temperature of the heated air dischargedfrom the front of the heater casing. Switch 32 is located in the stackwhere, at the beginning of operation, there will be a predeterminedminimum temperature rise, for example, 50", in one minute. This switchordinarily is closed, that is, when the stack is cold, and once theminimum temperature rise is attained, it opens and thereafter will notclose except upon a shutdown sufiiciently long to cause a temperaturedrop of about 50. However, this switch is arranged to be closed manuallywhen required.

Switch 26 is closed When cold and is located to be exposed to the heatfrom element 31. The fiow of current through the operating circuit ofrelay 28 causes heater 31 to heat switch 26. If switch 32 remains closeda predetermined minimum time, as for example seconds, the switch 26 isopened by the heat of element 31, thus opening the operating circuit ofthe relay 28 to open contacts 33 and deenergize the igniter and solenoid17, so that fuel flow to the burner stops. However, should switch 32 beopened by the predetermined stack temperature rise, the operatingcircuit of relay 28 is opened, but the relay is held in position by aholding circuit at reduced voltage comprising lead 36, contacts 35,leads 29, 27, switch 26 and lead 25. The opening of switch 32deenergizes heater 31 and switch 26 of the holding circuit remainsclosed. This is the normal operating condition.

However, should the burner fail to ignite, switch 32 remains closedbecause of the failure of the temperature to rise, and heater 31 causesswitch 26 to open, thus opening the circuit of the relay 28 to opencontacts 33 and deenergize the igniter at the same time that the fuel isshut off to the burner.

The switch 12, it will be observed, provides a sequence of operationinvolving first energization of motor 3 to operate the blower in housing4 and fan 6, then turning on the fuel supply to the burner andenergizing the igniter. By having the motor 3 operate first, the airwill scavenge the combustion chamber at the start. Thereafter the burneris ignited. A stop 38 limits turning of the switch contactor so that theswitch must be reversely turned to shut off the burner. Upon reverseturning, the fuel supply is first shut oir and then the motor 3 andblowers driven thereby are stopped. Normally there is suflicient manualdelay in turning from position A to position B, or in reverse operationfrom position B to position A, but if desired, the switch mayincorporate a conventional automatic delay mechanism.

I claim as my invention:

In an air heater: a fuel burner; a motor; a pump driven by said motorfor supplying fuel to said burner; electrically operated meanscontrolling flow of fuel from the pump to the burner; an igniteradjacent the burner; means driven by said motor to supply air to saidburner to support combustion; an actuating electric circuit for saidigniter and 3 I a said electrically operated means; means controllingsaid circuit including a relay coil having a main operating circuit inwhich are connected in series an electric heater, a normally closedtemperature responsive switch subject to be opened by the heat ofsaidelectric heater, and a normally closed combustion responsive switchcontrolling current flow through said electric heater, said combustionresponsive switch being located to be opened by the heat of the burnerand upon failure of the burner to ignite allowing a temperature rise ofsaid heater to open said temperature responsive switch to deenergizesaid relay coil; a holding circuit for said relay coil including saidtemperature responsive switch, whereby opening of said combustionresponsive switch to deenergize the main circuit leaves the holdingcircuit energized; a main switch having one contact for energizing saidmotor, and a sec ond contact for energizing said actuating circuit; amovable sweep contactor to successively and thereafter concurrentlyengage said contacts when operated in one direction to first energizethe motor and then energize said actuating circuit; and a stop to limitturning of the contactor, the reverse movement of said main switchacting to serially deenergize said actuating circuit and the motor.

References Cited in the file of this patent UNITED STATES PATENTS I2,020,710 Warner Nov. 12, 1935 2,034,311 Rubel Mar. 17, 1936 2,080,580Shaw May 18, 1937 2,188,565 Bower Jan. 30, 1940 2,427,675 HolthouseSept. 23, 1947 2,447,373 Smoot Aug. 17, 1948 2,469,271 Logan May 3, 19492,575,289 Nycum et al.' Nov. 13, 1951

